radar target vs radar echo

radar target and radar echo both are nouns.

Word	Noun	Adjective	Verb	Adverb
radar target	Yes	No	No	No
radar echo	Yes	No	No	No

As nouns, radar echo is a hypernym of radar target; that is, radar echo is a word with a broader meaning than radar target:

radar target: a radar echo displayed so as to show the position of a reflecting surface
radar echo: an electronic signal that has been reflected back to the radar antenna; contains information about the location and distance of the reflecting object

radar target (noun)	radar echo (noun)
a radar echo displayed so as to show the position of a reflecting surface	an electronic signal that has been reflected back to the radar antenna; contains information about the location and distance of the reflecting object